Jaundice is caused by high levels of a chemical called bilirubin in the baby's body.

Red blood cells are being made and being broken down continually in all people, including babies before and after birth. Haemoglobin in the red blood cells breaks down into smaller chemicals including bilirubin.

Before birth the bilirubin is carried out of the baby through the placenta, and into the mother's blood.

When a baby is born, the baby's liver suddenly has to take over the work of getting rid of bilirubin and it can take the liver a few days to fully manage this.

All babies have a raised bilirubin level for several days, but in healthy full term babies this may not be noticeable, or if it is, the level is usually still low and not a problem.

Some babies who have a lot of bruising when they are being born have a lot of damaged red blood cells (in the bruise) which need to be broken down, and these babies can develop a higher bilirubin level.

Some breast fed babies (about 5%) will have mild jaundice which can last for a few weeks.

There seems to be a protein in breastmilk which keeps bilirubin levels high enough to cause jaundice but not high enough to cause harm.

In the early days after birth, before the breast milk 'comes in' the baby may be getting less fluid and fewer calories than a bottle fed baby (this is not harmful) slowing down the elimination of bilirubin.

In some babies, especially premature babies, or ones who are sick for some other reason (eg they have an infection), the bilirubin level goes higher.

Some babies who have a blood group different to their mother's blood group may also have jaundice.

Babies with a moderate level of bilirubin may be a bit more sleepy than usual, and may not feed well. Encouraging them to feed more often is usually enough to keep their bilirubin levels down.

If the level of bilirubin in a baby's blood rises to an extremely high level, it will damage parts of the brain including parts that affect hearing, vision and control of movement (this is called kernicterus).

The level of bilirubin that will be harmful depends on how mature and how well the baby is. A large, full term, healthy baby can have a higher level without problems than can a sick or premature baby.

Since many babies are sent home within the first 2 days of life, parents will need to watch their baby for signs of jaundice.

Jaundice appears first on the face and head. If the level goes higher, it will appear on the body, and if it goes even higher it will be on the palms of the hands and soles of the feet.

A simple test is to gently press your fingertip on the tip of your child's nose or forehead. If, when you lift your fingertip off, the skin is white, there is no jaundice. If there is a yellowish colour, contact your doctor.

If a child appears to be jaundiced, a blood test can be done to work out the level of bilirubin, and the decision about treatment will depend on that level and how healthy the baby is.

Most babies who are well and who are mildly jaundiced will not need treatment. As the liver matures, it will break the bilirubin into other chemicals which can be passed out through the gut.

Phototherapy (or light therapy) may be used for babies whose level is getting higher. Light energy helps change the bilirubin that is just under the skin into a different chemical which is more easily passed out of the baby's body (excreted). Babies may need phototherapy for several days. Phototherapy is safe and effective.

Babies will be placed in a warm covered cot. They may be able to stay in their mother's room or they may need to be moved to the ward nursery.

They will have eye shields placed over their eyes.

They will be nursed naked so that the maximum amount of light can fall on their skin.

While they are having phototherapy they may need feeds more often. If breastfed, the baby should be put to the breast between 8-12 times per day for the first several days.

You will be encouraged to continue to care for your baby as much as possible.

Blood tests are usually done daily to work out if your baby still needs phototherapy.

If the levels of bilirubin get very high, the baby may need an exchange transfusion (the baby's blood is replaced with other blood, sometimes from the mother). This is rare.

Sunlight exposure is no longer recommended as a treatment for jaundice due to risk of sunburn or overheating.

If your baby is starting to look yellow, make sure the baby is checked by a doctor, midwife or child health nurse.

If your baby seems unwell (for example is not feeding well or has a fever), and is starting to look yellow, it is even more important to have the baby checked soon.

If your baby is well, is starting to look jaundiced and is being breast fed, it may be breast milk jaundice. Breast milk is still best for your baby. Increasing feeds may help. It is rare for a mother to need to stop breastfeeding. Check with your doctor, midwife or a lactation consultant before you do this.

If phototherapy lights are not available, putting a baby next to a window where there is lots of indirect light (not direct light from the sun) may be recommended, but this does not work as well as phototherapy.

Pregnancy, birth and baby Pregnancy, Birth and Baby is a national Australian Government service providing support and information for expecting parents and parents of children, from birth to 5 years of age. http://www.pregnancybirthbaby.org.au/